I have a struct that I want to turn into an EnvironmentObject so I can pass it to a child struct, but when I do, it crashes by saying MissingEnvironmentObjectError: Missing EnvironmentObject. My struct looks like:
class event: ObservableObject {
#Published var Name: String
#Published var CalendarID: Int
var timeStart: Date
var timeEnd: Date
var checklist = [checklistObject]()
init(_ eventName: String, _ calID: Int, _ timeStart: Date, _ timeEnd: Date) {
Name = eventName
CalendarID = calID
self.timeStart = timeStart
self.timeEnd = timeEnd
logger.log("Successfully created new event")
}
func newChecklistItem(Content: String){
checklist.append(checklistObject(Content, false))
}
func getChecklistSize() -> Int {
return checklist.count
}
}
and my program looks like:
import SwiftUI
struct checklistDisplayRow: View {
#EnvironmentObject var Event: event
var itemID: Int
init(itemID: Int){
self.itemID = itemID
Event.newChecklistItem(Content: "Stuff")
}
var body: some View {
HStack{
Toggle("", isOn: $Event.checklist[itemID].complete)
Text("hi")
}
}
}
struct checklistDisplayRow_Previews: PreviewProvider {
static var previews: some View {
checklistDisplayRow(itemID: 0)
.environmentObject(event("Title", 1, Date(timeIntervalSince1970: 1576800000), Date(timeIntervalSince1970: 1576800060)))
}
}
Thanks in advance for any help.
At the moment, you are setting the environment object for the preview, but you also need to set it in the hierarchy above where you are using checklistDisplayRow.
For example, if you were using a few checklistDisplayRows in a VStack (for the items in an event's checklist), you could do something like this:
VStack {
ForEach(checklist, id: \.id) { item in
checklistDisplayRow(itemID: item.id)
}
}.environmentObject(
event("Title", 1, Date(timeIntervalSince1970: 1576800000), Date(timeIntervalSince1970: 1576800060)
)
I hope that's helpful!
Related
I have a list of sliders, but I have a problem updating the text that shows the slider value.
The app workflow is like this:
User taps to add a new slider to the list.
An object that defines the slider is created and stored in an array.
The class that has the array as a property (Db) is an ObservableObject and triggers a View update for each new item.
The list is updated with a new row.
So far, so good. Each row has a slider whose value is stored in a property in an object in an array. However, the value text doesn't update as soon as the slider is moved, but when a new item is added. Please see the GIF below:
The Slider doesn't update the text value when moved
How can I bind the slider movements to the text value? I thought that by defining
#ObservedObject var slider_value: SliderVal = SliderVal()
and binding that variable to the slider, the value would be updated simultaneously but that is not the case. Thanks a lot for any help.
import SwiftUI
import Combine
struct ContentView: View {
#ObservedObject var db: Db
var body: some View {
NavigationView{
List(db.criteria_db){criteria in
VStack {
HStack{
Text(criteria.name).bold()
Spacer()
Text(String(criteria.slider_value.value)) //<-- Problem here
}
Slider(value: criteria.$slider_value.value, in:0...100, step: 1)
}
}
.navigationBarTitle("Criteria")
.navigationBarItems(trailing:
Button(action: {
Criteria.count += 1
db.criteria_db.append(Criteria(name: "Criteria\(Criteria.count)"))
dump(db.criteria_db)
}, label: {
Text("Add Criteria")
})
)
}
.listStyle(InsetGroupedListStyle())
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView(db: Db())
}
}
struct Criteria: Identifiable {
var id = UUID()
var name: String
#ObservedObject var slider_value: SliderVal = SliderVal()
static var count: Int = 0
init(name: String) {
self.name = name
}
}
class Db: ObservableObject {
#Published var criteria_db: [Criteria] = []
}
class SliderVal: ObservableObject {
#Published var value:Double = 50
}
The #ObservableObject won't work within a struct like that -- it's only useful inside a SwiftUI View or a DynamicProperty. With your use case, because the class is a reference type, the #Published property has no way of knowing that the SliderVal was changed, so the owner View never gets updated.
You can fix this by turning your model into a struct:
struct Criteria: Identifiable {
var id = UUID()
var name: String
var slider_value: SliderVal = SliderVal()
static var count: Int = 0
init(name: String) {
self.name = name
}
}
struct SliderVal {
var value:Double = 50
}
The problem, once you do this, is you don't have a Binding to use in your List. If you're lucky enough to be on SwiftUI 3.0 (iOS 15 or macOS 12), you can use $criteria within your list to get a binding to the element being currently iterated over.
If you're on an earlier version, you'll need to either use indexes to iterate over the items, or, my favorite, create a custom binding that is tied to the id of the item. It looks like this:
struct ContentView: View {
#ObservedObject var db: Db = Db()
private func bindingForId(id: UUID) -> Binding<Criteria> {
.init {
db.criteria_db.first { $0.id == id } ?? Criteria(name: "")
} set: { newValue in
db.criteria_db = db.criteria_db.map {
$0.id == id ? newValue : $0
}
}
}
var body: some View {
NavigationView{
List(db.criteria_db){criteria in
VStack {
HStack{
Text(criteria.name).bold()
Spacer()
Text(String(criteria.slider_value.value))
}
Slider(value: bindingForId(id: criteria.id).slider_value.value, in:0...100, step: 1)
}
}
.navigationBarTitle("Criteria")
.navigationBarItems(trailing:
Button(action: {
Criteria.count += 1
db.criteria_db.append(Criteria(name: "Criteria\(Criteria.count)"))
dump(db.criteria_db)
}, label: {
Text("Add Criteria")
})
)
}
.listStyle(InsetGroupedListStyle())
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView(db: Db())
}
}
class Db: ObservableObject {
#Published var criteria_db: [Criteria] = []
}
Now, because the models are all value types (structs), the View and #Published know when to update and your sliders work as expected.
try something like this:
Slider(value: criteria.$slider_value.value, in:0...100, step: 1)
.onChange(of: criteria.slider_value.value) { newVal in
DispatchQueue.main.async {
criteria.slider_value.value = newVal
}
}
I came across a situation that you use class data as your data source, and display them in a swiftUI list view, when you update your data source, the swiftUI list view won't be updated, what can we do to make the class data updates interactive with swiftUI?
see code blow:
I define the environment object :
import Foundation
import Combine
class DataSource: ObservableObject {
public static let shared = DataSource()
#Published var datalist: [RowData] = []
func fetch() -> Void {
for n in 1...50 {
let data = RowData(title: "Index:\(n)", count: 0)
datalist.insert(data, at: 0)
}
}
func update() {
for data in datalist {
data.count = data.count+1
print("\(data.title) update count to :\(data.count)")
data.objectWillChange.send()
}
self.objectWillChange.send()
}
}
to display each data in a Row View:
import SwiftUI
struct RowView: View {
#State var data: RowData
var body: some View {
HStack{
Text(data.title)
Spacer()
Text("\(data.count)")
}.padding()
}
}
struct RowView_Previews: PreviewProvider {
static var previews: some View {
RowView(data: RowData(title: "text", count: 1))
}
}
class RowData: ObservableObject {
var title: String = ""
var count: Int = 0
init(title: String, count: Int) {
self.title = title
self.count = count
}
}
in content view, display the data in a list view, I would like to refresh all the view updates when click update button. the button triggers the update methods to update the class data value from data source.
struct ContentView: View {
#EnvironmentObject var data: DataSource
#State var shouldUpdate:Bool = false
#State var localData:[RowData] = []
var body: some View {
VStack {
Button(action: {
// your action here
self.data.update()
self.shouldUpdate.toggle()
self.localData.removeAll()
self.localData = self.data.datalist
}) {
Text("update")
}
List {
ForEach(0..<self.localData.count, id:\.self) { index in
RowView(data: self.localData[index])
}
}
}
}
}
Well... I don't see the reason to have localData, but, anyway, here is modified code that works.
Tested with Xcode 12 / iOS 14
class DataSource: ObservableObject {
public static let shared = DataSource()
#Published var datalist: [RowData] = []
func fetch() -> Void {
for n in 1...50 {
let data = RowData(title: "Index:\(n)", count: 0)
datalist.insert(data, at: 0)
}
}
func update() {
for data in datalist {
data.count = data.count+1
print("\(data.title) update count to :\(data.count)")
}
self.objectWillChange.send()
}
}
struct RowView: View {
#ObservedObject var data: RowData
var body: some View {
HStack{
Text(data.title)
Spacer()
Text("\(data.count)")
}.padding()
}
}
class RowData: ObservableObject {
#Published var title: String = ""
#Published var count: Int = 0
init(title: String, count: Int) {
self.title = title
self.count = count
}
}
struct ContentView: View {
#EnvironmentObject var data: DataSource
#State var localData:[RowData] = []
var body: some View {
VStack {
Button(action: {
// your action here
self.data.update()
self.localData = self.data.datalist
}) {
Text("update")
}
List {
ForEach(0..<self.localData.count, id:\.self) { index in
RowView(data: self.localData[index])
}
}
}
.onAppear {
self.data.fetch()
self.localData = self.data.datalist
}
}
}
I'm trying to fill up a Picker with data fetched asynchronously from external API.
This is my model:
struct AppModel: Identifiable {
var id = UUID()
var appId: String
var appBundleId : String
var appName: String
var appSKU: String
}
The class that fetches data and publish is:
class AppViewModel: ObservableObject {
private var appStoreProvider: AppProvider? = AppProvider()
#Published private(set) var listOfApps: [AppModel] = []
#Published private(set) var loading = false
fileprivate func fetchAppList() {
self.loading = true
appStoreProvider?.dataProviderAppList { [weak self] (appList: [AppModel]) in
guard let self = self else {return}
DispatchQueue.main.async() {
self.listOfApps = appList
self.loading = false
}
}
}
init() {
fetchAppList()
}
}
The View is:
struct AppView: View {
#ObservedObject var appViewModel: AppViewModel = AppViewModel()
#State private var selectedApp = 0
var body: some View {
ActivityIndicatorView(isShowing: self.appViewModel.loading) {
VStack{
// The Picker doesn't bind with appViewModel
Picker(selection: self.$selectedApp, label: Text("")) {
ForEach(self.appViewModel.listOfApps){ app in
Text(app.appName).tag(app.appName)
}
}
// The List correctly binds with appViewModel
List {
ForEach(self.appViewModel.listOfApps){ app in
Text(app.appName.capitalized)
}
}
}
}
}
}
While the List view binds with the observed object appViewModel, the Picker doesn't behave in the same way. I can't realize why. Any help ?
I filed bug report, FB7670992. Apple responded yesterday, suggesting that I confirm this behavior in iOS 14, beta 1. It appears to now have been resolved.
struct ContentView: View {
#ObservedObject var viewModel = ViewModel()
var body: some View {
Picker("", selection: $viewModel.wheelPickerValue) {
ForEach(viewModel.objects) { object in
Text(object.string)
}
}
.pickerStyle(WheelPickerStyle())
.labelsHidden()
}
}
Where
struct Object: Identifiable {
let id = UUID().uuidString
let string: String
}
class ViewModel: ObservableObject {
private var counter = 0
#Published private(set) var objects: [Object] = []
#Published var segmentedPickerValue: String = ""
#Published var wheelPickerValue: String = ""
fileprivate func nextSetOfValues() {
let newCounter = counter + 3
objects = (counter..<newCounter).map { value in Object(string: "\(value)") }
let id = objects.first?.id ?? ""
segmentedPickerValue = id
wheelPickerValue = id
counter = newCounter
}
init() {
let timer = Timer.scheduledTimer(withTimeInterval: 2, repeats: true) { [weak self] timer in
guard let self = self else { timer.invalidate(); return }
self.nextSetOfValues()
}
timer.fire()
}
}
Results in:
I can't put this into your code because it is incomplete but here is a sample.
Pickers aren't meant to be dynamic. They have to be completely reloaded.
class DynamicPickerViewModel: ObservableObject {
#Published private(set) var listOfApps: [YourModel] = []
#Published private(set) var loading = false
fileprivate func fetchAppList() {
loading = true
DispatchQueue.main.async() {
self.listOfApps.append(YourModel.addSample())
self.loading = false
}
}
init() {
fetchAppList()
}
}
struct DynamicPicker: View {
#ObservedObject var vm = DynamicPickerViewModel()
#State private var selectedApp = ""
var body: some View {
VStack{
//Use your loading var to reload the picker when it is done
if !vm.loading{
//Picker is not meant to be dynamic, it needs to be completly reloaded
Picker(selection: self.$selectedApp, label: Text("")) {
ForEach(self.vm.listOfApps){ app in
Text(app.name!).tag(app.name!)
}
}
}//else - needs a view while the list is being loaded/loading = true
List {
ForEach(self.vm.listOfApps){ app in
Text(app.name!.capitalized)
}
}
Button(action: {
self.vm.fetchAppList()
}, label: {Text("fetch")})
}
}
}
struct DynamicPicker_Previews: PreviewProvider {
static var previews: some View {
DynamicPicker()
}
}
I have the following model object that I use to populate a List with a Toggle for each row, which is bound to measurement.isSelected
final class Model: ObservableObject {
struct Measurement: Identifiable {
var id = UUID()
let name: String
var isSelected: Binding<Bool>
var selected: Bool = false
init(name: String) {
self.name = name
let selected = CurrentValueSubject<Bool, Never>(false)
self.isSelected = Binding<Bool>(get: { selected.value }, set: { selected.value = $0 })
}
}
#Published var measurements: [Measurement]
#Published var hasSelection: Bool = false // How to set this?
init(measurements: [Measurement]) {
self.measurements = measurements
}
}
I'd like the hasSelection property to be true whenever any measurement.isSelected is true. I'm guessing somehow Model needs to observe changes in measurements and then update its hasSelection property… but I've no idea where to start!
The idea is that hasSelection will be bound to a Button to enable or disable it.
Model is used as follows…
struct MeasurementsView: View {
#ObservedObject var model: Model
var body: some View {
NavigationView {
List(model.measurements) { measurement in
MeasurementView(measurement: measurement)
}
.navigationBarTitle("Select Measurements")
.navigationBarItems(trailing: NavigationLink(destination: NextView(), isActive: $model.hasSelection, label: {
Text("Next")
}))
}
}
}
struct MeasurementView: View {
let measurement: Model.Measurement
var body: some View {
HStack {
Text(measurement.name)
.font(.subheadline)
Spacer()
Toggle(measurement.name, isOn: measurement.isSelected)
.labelsHidden()
}
}
}
For info, here's a screenshot of what I'm trying to achieve. A list of selectable items, with a navigation link that is enabled when one or more is selected, and disabled when no items are selected.
#user3441734 hasSelection should ideally be a get only property, that
is true if any of measurement.isSelected is true
struct Data {
var bool: Bool
}
class Model: ObservableObject {
#Published var arr: [Data] = []
var anyTrue: Bool {
arr.map{$0.bool}.contains(true)
}
}
example (as before) copy - paste - run
import SwiftUI
struct Data: Identifiable {
let id = UUID()
var name: String
var on_off: Bool
}
class Model: ObservableObject {
#Published var data = [Data(name: "alfa", on_off: false), Data(name: "beta", on_off: false), Data(name: "gama", on_off: false)]
var bool: Bool {
data.map {$0.on_off} .contains(true)
}
}
struct ContentView: View {
#ObservedObject var model = Model()
var body: some View {
VStack {
List(0 ..< model.data.count) { idx in
HStack {
Text(verbatim: self.model.data[idx].name)
Toggle(isOn: self.$model.data[idx].on_off) {
EmptyView()
}
}
}
Text("\(model.bool.description)").font(.largeTitle).padding()
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
When the model.data is updated
#Published var data ....
its publisher calls objectWillChange on ObservableObject.
Next SwiftUI recognize that ObservedObject needs the View to be "updated". The View is recreated, and that will force the model.bool.description will have fresh value.
LAST UPDATE
change this part of code
struct ContentView: View {
#ObservedObject var model = Model()
var body: some View {
NavigationView {
List(0 ..< model.data.count) { idx in
HStack {
Text(verbatim: self.model.data[idx].name)
Toggle(isOn: self.$model.data[idx].on_off) {
EmptyView()
}
}
}.navigationBarTitle("List")
.navigationBarItems(trailing:
NavigationLink(destination: Text("next"), label: {
Text("Next")
}).disabled(!model.bool)
)
}
}
}
and it is EXACTLY, WHAT YOU HAVE in your updated question
Try it on real device, otherwise the NavigationLink is usable only once (this is well known simulator bug in current Xcode 11.3.1 (11C504)).
The problem with your code at the moment is that even if you observe the changes to measurements, they will not get updated when the selection updates, because you declared the var isSelected: Binding<Bool> as a Binding. This means that SwiftUI is storing it outside of your struct, and the struct itself doesn't update (stays immutable).
What you could try instead is declaring #Published var selectedMeasurementId: UUID? = nil on your model So your code would be something like this:
import SwiftUI
import Combine
struct NextView: View {
var body: some View {
Text("Next View")
}
}
struct MeasurementsView: View {
#ObservedObject var model: Model
var body: some View {
let hasSelection = Binding<Bool> (
get: {
self.model.selectedMeasurementId != nil
},
set: { value in
self.model.selectedMeasurementId = nil
}
)
return NavigationView {
List(model.measurements) { measurement in
MeasurementView(measurement: measurement, selectedMeasurementId: self.$model.selectedMeasurementId)
}
.navigationBarTitle("Select Measurements")
.navigationBarItems(trailing: NavigationLink(destination: NextView(), isActive: hasSelection, label: {
Text("Next")
}))
}
}
}
struct MeasurementView: View {
let measurement: Model.Measurement
#Binding var selectedMeasurementId: UUID?
var body: some View {
let isSelected = Binding<Bool>(
get: {
self.selectedMeasurementId == self.measurement.id
},
set: { value in
if value {
self.selectedMeasurementId = self.measurement.id
} else {
self.selectedMeasurementId = nil
}
}
)
return HStack {
Text(measurement.name)
.font(.subheadline)
Spacer()
Toggle(measurement.name, isOn: isSelected)
.labelsHidden()
}
}
}
final class Model: ObservableObject {
#Published var selectedMeasurementId: UUID? = nil
struct Measurement: Identifiable {
var id = UUID()
let name: String
init(name: String) {
self.name = name
}
}
#Published var measurements: [Measurement]
init(measurements: [Measurement]) {
self.measurements = measurements
}
}
I'm not sure exactly how you want the navigation button in the navbar to behave. For now I just set the selection to nil when it's tapped. You can modify it depending on what you want to do.
If you want to support multi-selection, you can use a Set of selected ids instead.
Also, seems like the iOS simulator has some problems with navigation, but I tested on a physical device and it worked.
So I'm getting the error Unknown attribute ObservableObject next to the #ObservableObject var dataSource = DataSource() call below. the ObservableObject worked perfectly a couple days ago in another project but not anymore.
import SwiftUI
import Combine
class DataSource: ObservableObject {
var willChange = PassthroughSubject<Void,Never>()
var expenses = [Expense]() {
willSet { willChange.send() }
}
var savingsItems = [SavingsItem](){
willSet { willChange.send() }
}
//#State var monthlyIncomeText: String
//var monthlyIncome: Int = 1364
init(){
addNewExpense(withName: "Spotify", price: 14)
}
func addNewExpense(withName name: String, price: Int){
let newExpense = Expense(name: name, price: price)
expenses.append(newExpense)
}
func addNewSavingsItem(withName name: String, price: Int, percentage: Double){
let newSavingsItem = SavingsItem(name: name, price: price, timeTilCompletion: 0, percentage: percentage)
savingsItems.append(newSavingsItem)
}
}
struct ContentView: View {
#ObservableObject var dataSource = DataSource()
var body: some View {
VStack{
Text("Expenses")
List(dataSource.expenses) { expense in
ExpenseRow(expense: expense)
}
}
}
}
Could anyone help?
ObservableObject is a protocol that ObservedObjects must conform to. See here for documentation on ObservableObject, and here for documentation on ObservedObject, which is the property wrapper that you are looking for. Change your ContentView code to this:
struct ContentView: View {
#ObservedObject var dataSource = DataSource()
var body: some View {
VStack {
Text("Expenses")
List(dataSource.expenses) { expense in
ExpenseRow(expense: expense)
}
}
}
}